Tobold's Blog
Tuesday, August 22, 2017
 
Retraction

For weeks I have been having problems with my XYZ Da Vinci Jr. 1.0w 3D printer. Some prints work just fine, while other fail. Even worse, some prints which work fine if I try to print a single figurine then fail if I try to print multiple copies at the same time. It was driving me crazy, until with a lot of testing and observing I finally found out what the problem is: Retraction.

So what is retraction in 3D printing? Imagine printing a model of the Eiffel Tower. There is a lot of empty space in such a model. Because the print is done layer by layer, from the bottom up, the print head has to print a small thickness where a girder is, then move without printing to the next girder. In order to prevent PLA from coming out of the print head and causing strings to appear between the girders, the stepper motor is pulling the filament back a little bit before moving. That pulling back is called retraction.

Now what is happening with my printer, and I am not 100% sure how or why, is that the stepper motor is more efficient during retraction than during moving the filament forward. It basically retracts too much, and then after the movement pushes forward the filament by too little. So if I print a piece with lots of empty spaces and lots of retraction happening, while the solid sections are relatively thin, I end up retracting more and more, until the end of the filament has completely left the hot part of the extruder head. While the print head is still moving, there is no more plastic coming out of the nozzle at all, and the print fails.

Now there is a lot of 3D printing software with millions of settings where you can change the setting for retraction. Unfortunately the XYZ Printers don't work with any of those 3D printing programs. They only work with their proprietary XYZWare. Which is deliberately simplified to make "plug and play" printing for the average customer possible. Somewhere in the depths of the code there must be a retraction setting (you can observe the filament moving backwards), but there is no way to access or change that setting. And I don't want to "jailbreak" my 3D printer with some modified firmware, because that has the potential to completely break it.

Right now my solution is simply to avoid printing models with too much empty space in them. That means printing miniatures one by one instead of in batches, which would be more practical for prints during the night. But the long-term solution will be buying a better 3D printer which isn't so limited with what software I can use, and what settings I can change. Right now I am thinking of still waiting a bit with that, as I haven't found the printer of my dreams yet. One important feature for me is being able to print via WiFi, and surprisingly few printers have that. I want a pre-assembled 3D printer with a sturdy frame, not a wobbly self-assembly kit. But of course I don't want to spend a fortune on it either. My $500 printer is maybe not high enough quality, but I wouldn't want to spend more than $2,000 even on a good printer. As the market is developing, I might find the printer I want next year.

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Comments:
Alas, the Ultimaker 3 is sitting at $3.5k, so I'd have to agree with putting up with your current device for now. If your budget box decides to quit entirely, you may want to look at a Prusa i3 Mk2 printer ($899 assembled and tested). It's open source and made in Europe. The Prusa is more of an enthusiast's 3d printer, but you're no longer a beginner.
 
Isn't that exactly the sort of thing the manufacturer should be doing their best to fix ASAP via an official firmware upgrade? Are they aware of this problem? Is you unit unusual, or do they all have such a serious flaw?
 
The XYZ Da Vinci Jr. is the cheapest 3d printer you can buy. The manufacturer doesn't care about minor flaws like Tobold describes - they're too busy making more and selling them. The only support available is fellow sufferers on forums.

This is an emerging technology. In a few years, the price will be down substantially and the quality will be much better. XYZ will probably be out of business then, so they're selling cheap (in every sense of the word) hardware that runs only on their software and only uses their ABS, making as much money as they can before someone else runs them out of business.
 
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